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Lec. 2 History of Evolutionary Theory
Transcript of Lec. 2 History of Evolutionary Theory
5 Contributing Disciplines
Geology-Study of rock formation and change
Paleontology-Study of fossils
Taxonomy-Classification of organisms
Systematics-Study of biological relationships
Demography-Study of population composition
Evolution: a sequence of change over time
Evolution is both fact & theory
Fact: We have fossil evidence showing it happened
Theory: Uncertainty about speed at which change occurs
For a trait to be evolutionary, it must be INHERITABLE
Pre-17th Century/Pre-evolutionary Theory
Bishop James Ussher
Most believe in Special Creation
Biology teach creationism
Literal interpretations of the bible
God made the Earth
God made man in his image
Great Chain of Being
Man has dominion over all the plants and animals
John begat Paul
Determines the Earth
was made 4004 BC
Thursday Oct. 23
I told you it was very literal interpretation
Sir Francis Bacon
theory, but this
is the basis for
If you hate science,
3 KEY Concepts before
Evolutionary Theory is
The Earth is Ancient
Earth's surface has and continues to change
Plants and animals have and continue to change
Early Evolutionary Theory
If discussed it is highly contentious
Often secretive and obscure
Ex. Poem by Erasmus Darwin (grandfather to Charlie)
THE TEMPLE OF NATURE
Organic life beneath the shoreless waves
Was born and nurs'd in ocean's pearly caves;
First forms minute, unseen by spheric glass,
Move on the mud, or pierce the watery mass;
There as successive generations bloom,
New powers acquire and larger limbs assume;
Whence countless groups of vegetation spring,
And breathing realms of fin and feet and wing
Fossils are found and can't be explained
God made everything, but fossils don't look like anything living
What are they?
Paleontology studies fossils
Studies tissue structure of fossilized wood
Fossil wood had same tissue as living trees
Determines fossils were once living
Fossils are the remains of organisms
Baron George Cuvier
Studied fossil animals in France
Father of comparative anatomy
Father of vertebrate paleontology
Explains existence of fossils through Catastrophism:
After catastrophic events (earthquakes, floods, etc) all life in the region was wiped out; eventually it is repopulated by animals from other locations
Catastrophism fits with bible (floods like Noah's Arc) and therefore accepted. We now know it was wrong.
Taxonomy and Systematics
Fossils are worldwide
Insatiable human need to classify
Paleontology allows us to determine biological relationships
Fathers of Taxonomy:
Looked at complete morphology
Similar features means similar classification
Studied plant sex organs
Developed a hierarchy
Naming system called Binomial Nomenclature (still used today!)
Published in Systemae Naturae 1735
Two Latin Names that describe the organism
Genus: Group of species with similar adaptations
Species: Populations whose members can naturally interbreed and produce
*note, Genus species is always written in italics or underlined and the first letter of the Genus is the only one capitalized
The Liger is an offspring of a lion and tiger.
Ligers generally are infertile and therefore lions and tigers are separate species. Other famous example...Mule!
Jumping to Conclusions
There is proof of animals changing
Incomplete puzzle, still missing Earth is old and Earth surface has changed
Belief is that fossils are dead animals & all animals were created and existed at the same time
Jean Baptiste Lamarck
Published 'Philosopha Zoologique'
Good ideas about evolution
Life-forms reproduce and pass on modifications/changes to offspring
Changes occur because organism want it
Any change is passed on to offspring
Lamarck's Giraffe Example
Living organisms arose from precursor species
The change is related to the environment of the organism
Change does not occur in 1 lifetime
Change is not directed by 'will'
No inheritance of acquired characteristics
How do you know Lamarck was wrong?
Example 1: If you were to cut off a mouse's tail, Lamarckian evolution claims all its babies will be missing a tail.
Example 2: If you get a tatoo, Lamarckian evolution says your babies will have the same tatoo.
Obviously both of these are false, therefore Lamarck was wrong. This was recognized during his time. He lost all credibility and died a pauper.
Studying rock formations and changes
Because of Geology the last two concepts are realized:
Earth is ancient
Surface of the Earth has changed
Once established evolution can be accepted (by some)
Studies wind and rain erosion
Figured out Earth's surface was changing through erosion
Determined Earth was really old, looked at strata and calculated it to millions of years (still short of 4.6billion years we know today)
Came up with the theory of Uniformitarianism
The same processes (erosion, deposition, etc) happening today happened in the past and will continue to happen
He lost credibility and called a heretic because his ideas went against bible and catastrophism
Also studies erosion
Writes the book 'Principles of Geology'
So well researched that uniformitarianism becomes prominent and catastrophism is rejected
His book is what Charles Darwin reads and helps convince him the Earth is really old and was not made by God.
FOUNDATION IS SET FOR EVOLUTIONARY THEORY
Brought up in a religious family
Almost became a priest
Studied to be a Naturalist/Biologist
Classes taught creationist ideas
He had to change everything he believed in and learned in school to create evolutionary theory!
After school, a 22yr old Darwin gets a job as a naturalist on the HMS Beagle, a 5 year journey.
He collects specimens and takes detailed notes on plants and animals.
Reads Lyell's book and, after returning to England, befriends Lyell.
Becomes a prominent member of the British scientific community.
Would not publish his work, felt like something was missing and wanted a magnum opus (large collection of work that can't be disproved).
Then he reads an essay by Thomas Maltheus (a demographer).
Writes about supply and demand
Populations are limited by resources
Not enough food to support ever growing population
Populations will compete for resources
Those that are best suited for the competition will get resources and survive; others who can't compete will die
These ideas are directly used by Darwin
Despite reading Maltheus, Darwin still doesn't write.
Waits and collects data.
Finally publishes 'On the Origin of Species by Natural Selection' in 1859, 23 years after the Beagle
He waited because so many people lost credibility with non-creationist ideas.
The push he got was from...
Alfred Russell Wallace
Wallace first worked in the Amazon River Basin
Later worked in the Malay Archipelago
Also reads Lyell's 'Principles of Geology' and Maltheus' essay
Develops his own ideas of Evolution, almost identical to Darwin
Since he was just making his name, he writes a well-known naturalist....DARWIN!
Darwin reads identical ideas from Wallace and is prompted by Lyell to finally publish
Darwin and Wallace agree to co-publish on the Theory of Evolution in an essay
Raise your hand if you knew who Wallace was?
Darwin's social and scientific status was greater than Wallace's
Wallace gained higher scientific status
Darwin gets most of the credit because he had so much data and had the idea first
DARWIN'S CONTRIBUTIONS TO EVOLUTIONARY THEORY
Evolution has occurred
Evolution is a gradual change
Natural Selection is Darwin's term
Speciation has happened
The Descent of Man
Published 12yrs after 'Origins'
Waited so long because he wanted to make sure people were accepting of evolution before he suggested humans were not made in God's image
We will discuss Natural Selection and Speciation in more detail later.
Despite his well researched theory, there were still problems.
Lord Kelvin calculated the earth to be much younger than Darwin stated
Fleming Jenkins, like most everyone else at that time, believed inherited traits were a blend between parents and therefore couldn't be passed on without changing.
(if you want to read more http://orgs.usd.edu/esci/age/content/failed_scientific_clocks/kelvin_cooling.html)
One of Darwin's staunchest defenders
Frequently argued for Darwin and the theory of evolution
Took on Lord Kelvin and Fleeming Jenkins
Earned the nickname:
What Darwin really needed was an understanding of genetics and how traits are inherited
He was missing the work of Gregor Mendel, a Moravian monk (modern day Czech Republic)
Experimented for 8 years with 28,000 plants, creating purebreds and hybrids
He was the father of genetics but completely unknown
Figured out that traits DO NOT BLEND!
Eventually Mendel's work is rediscovered.
Julian Huxley, the grandson to Thomas Huxley, synthesizes genetics and evolutionary theory (one of many).
Having genetics makes inheritance work for evolutionary theory
The Structure of DNA
Rosalind Franklin & Raymond Gosling
Took x-ray images of DNA
Work went unpublished until
James Watson & Francis Crick
Relied heavily on work from Franklin and Gosling
Published that DNA had double helix shape
Important because it explains how so much information is contained within each cell
Morale: publish your work if you want credit!
Niles Eldredge and Stephen J. Gould
Found holes in the evolutionary record.
Published a paper on 'Punctuated Equilibria'.
This theory states that evolution is not a gradual change, but rather fast change with periods of stasis where nothing happens.